The 20 year-old Jeju United player has passed a medical and will now link up with the Bundesliga club in January.
He will stay until December 2014 and the move could then be made permanent if he impresses during his stint in Germany.
The striker revealed that compatriot Son Heung-Min was a key factor in helping him choose Leverkusen over other potential suitors.
"It's a great feeling to be playing here," he told Bild.
"Son is an important reason why I'm here. He only told me good things about the club. He will help me settle in."
Ryu will join the travelling squad for Leverkusen's away fixture at Werder Bremen on Saturday before returning to South Korea.